FIELD OF THE INVENTION
The invention relates to a chip card for the contactless transmission of electric signals to a terminal, including a card body in which a coupling element having conductor tracks and contact connections, and a semiconductor chip having an electronic circuit associated with the coupling element, are constructed in an integrated manner, contact elements provided on the surface of the semiconductor chip for electrical connection of the electronic circuit and the contact connections of the coupling element, and a carrier of an electrically insulating material supporting at least part of the conductor tracks and the contact connections of the coupling element. The invention also relates to a method of manufacturing such a chip card.
A contactless chip card as described above has become known from Published European Patent Application 671 705 A, in which an electrical connection between a coupling element and a semiconductor chip is achieved by using bonding wires and connecting pieces penetrating a carrier layer and provided with angled connecting surfaces.
Possible applications of chip cards, which are generally constructed in a check card format, have become extremely widespread because of a high functional flexibility and are increasing further with rising computing power and memory capacity of available integrated circuits. In addition to the fields of application which are typical at present for such chip cards in the form of health insurance cards, flex-time registration cards and telephone cards, the future will yield applications in electronic payment transactions, in computer-aided access control, in protected data memories and the like, in particular.
With regard to the type of coupling to a terminal or a reader, a distinction is drawn between chip cards having contacts and so-called contactless chip cards. In the case of a chip card having contacts, contact is made through the use of a metallic contact field having contact elements which are usually standardized in accordance with an ISO standard. The reliability of chip cards having contacts has been able to be continuously improved in previous years because of the increasing production experience of manufacturers. As a result, for example, the failure rate of telephone cards with a lifetime of one year is nowadays distinctly below one per thousand. Nevertheless, contacts are still one of the most frequent sources of faults in electromechanical systems.
Disturbances can be produced, for example, by contamination or wear of the contacts. Vibration can lead to short-term contact interruptions in the case of employment in mobile devices. Since the contacts on the surface of the chip card have to be connected directly to the inputs of the integrated circuit, there is, furthermore, the risk that electrostatic discharges may weaken or even destroy the integrated circuit in the interior of the card. Those technical problems are circumvented by the contactless chip card. In addition to those technical advantages, the contactless chip card furthermore offers a series of interesting new possibilities of applications for the card issuer and the card user. Thus, for example, contactless chip cards do not necessarily have to be inserted into a card reader. Instead, there are systems which function over a distance of up to one meter.
One broad field of application is represented, for example, by public local personal transport, where as many persons as possible have to be registered in as short a time as possible.
In addition to further advantages, the contactless chip card offers the advantage of ensuring that no technical elements are visible on the card surface, with the result that the visual configuration of the card surface is not restricted by magnetic strips or contact areas.
The disadvantages in the case of contactless chip cards which are available at present primarily reside in the additional components, such as transmission coils or capacitor plates, which have to be integrated into the card. That leads to the fact that, up until now, the manufacture of contactless chip cards has been distinctly more expensive than the comparable cards having contacts. Furthermore, the electronics which is necessary in the contactless chip card for the contactless transmission of electric signals to the terminal is more complicated. In principle, circuits which are suitable therefor are those which enable signal transmission through the use of microwaves, optical signals, capacitive or inductive coupling. The capacitive and the inductive coupling are most suitable because of the flat structural shape of the chip card. At present, in the case of most contactless cards, the transmission is carried out in an inductive manner, with which both the data and the power transmission may be realized. Thus, one or more induction coils are constructed in an integrated manner in the card body as coupling elements. The transmission of electric signals is carried out according to the principle of the loosely coupled transformer. The carrier frequency lies, for example, in the range between 100 and 300 kHz or at a few MHz, in particular the industrial frequency of 13.56 MHz. For that purpose, induction coils are needed which have coil areas that are typically about 30 to 40 cm.sup.2. That is significantly larger than the base area of the semiconductor chip which is on the order of magnitude of about 10 mm.sup.2. The induction coils have to be contacted in a suitable manner by the circuit which is located on the semiconductor chip. In that case, the semiconductor components are assembled onto the etched coil in the form of prefabricated modules or directly as a chip. The chip module which is present as a separate assembly, together with the induction coil which generally has only a few turns and has a flat construction, is laminated into the card body in order to complete the chip card. Intermediate foils, if appropriate, are provided with stampings being fitted as inlay foils for equalizing the volume during the lamination.